Vaccines

What Are Vaccines And What Do They Do?

A vaccine—also called a “shot” or “immunization”—is a substance that teaches your body's immune system to recognize and defend against harmful viruses or bacteria before you get infected. These are called “preventive vaccines” or “prophylactic vaccines,” and you get them while you are healthy. This allows your body to set up defenses against those dangers ahead of time. That way, you won't get sick if you're exposed to them later. Preventive vaccines are widely used to prevent diseases like polio, chicken pox, measles, mumps, rubella, influenza (flu), and hepatitis A and B.

In addition to preventive vaccines, there are also therapeutic vaccines. These are vaccines that are designed to treat people who already have a disease. Some scientists prefer to refer to therapeutic vaccines as “therapeutic immunogens.” Currently, there is only one FDA-approved therapeutic vaccine for advanced prostate cancer in men.

Is There A Vaccine For HIV?

No. There is currently no vaccine that will prevent HIV infection or treat those who have it.

Why Do We Need An HIV Vaccine?

Today, more people living with HIV have access to life-saving antiretroviral therapy (ART) than ever before, which is good for their health and reduces the likelihood that they will transmit the virus to others if they adhere to their HIV medication. In addition, others who are at high risk for HIV infection have access to Pre-exposure Prophylaxis (PrEP), or ART being used to prevent HIV. Yet, unfortunately, approximately 50,000 Americans and 2.3 million people worldwide still become newly HIV-infected each year. To control and ultimately end HIV globally, we need a powerful array of HIV prevention tools that are widely accessible to all who would benefit from them.

Vaccines historically have been the most effective means to prevent and even eradicate infectious diseases. They safely and cost-effectively prevent illness, disability and death. Like smallpox and polio vaccines, a preventive HIV vaccine could help save millions of lives.

Developing safe, effective and affordable vaccines that can prevent HIV infection in uninfected people is the best hope for controlling and/or ending the HIV epidemic.

The long-term goal is to develop a safe and effective vaccine that protects people worldwide from getting infected with HIV. However, even if a vaccine only protects some people, it could still have a major impact on the rates of transmission and help control the epidemic, particularly for populations where there is a high rate of HIV transmission. A partially effective vaccine could decrease the number of people who get infected with HIV, further reducing the number of people who can pass the virus on to others.

A therapeutic immunogen could also be beneficial for people living with HIV by helping slow the progression of the disease and prevent or delay the onset of AIDS.

For more information, see the video below with Dr. Anthony Fauci, Director of NIH’s National Institute of Allergy and Infectious Diseases (NIAID).

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Why Don't We Have An HIV Vaccine Yet?

HIV is a very complex, highly changeable virus, which makes speedy development of a successful preventive HIV vaccine very difficult, but not impossible. It also takes many years to conduct the research, including the careful clinical testing that will lead to a safe and effective vaccine.

Researchers from around the world have been working for more than two decades to create a vaccine that will protect people against HIV infection. NIAID supports the HIV Vaccine Trials Network (HVTN), an international collaboration of scientists and educators searching for an effective and safe HIV vaccine. The U.S. Military HIV Research Program (MHRP) is also engaged in HIV vaccine research and led a large collaboration of clinical scientists also funded by NIAID in implementing a vaccine trial that showed for the first time that an HIV vaccine is possible. (For more on this trial, see “What’s the Latest on HIV Vaccine Research,” below.)

How Is HIV Different From Other Viruses?

In part, HIV is different from other viruses because your immune system never fully gets rid of it. Most people who are infected with a virus recover from the infection, and their immune systems "clear" the virus from their bodies. This is true even for viruses that can be deadly, like influenza.

Once your body has cleared a particular virus, you often develop immunity to it—meaning it won’t make you sick the next time you are exposed to it. We’ve known since the late 1700s that you can create immunity by exposing people to dead or weakened viruses that will protect them from deadly diseases later.

But the human body can't seem to fully clear HIV and develop immunity to it. The antibodies your immune system makes to fight HIV are not effective—and HIV actually targets, invades, and then destroys some of the most important cells in your immune system itself. This means that, over time, HIV does serious damage to your body's ability to fight disease.

So far, no person with an established HIV infection has managed to clear the virus naturally. This has made it more difficult to develop a preventive HIV vaccine.

What’s The Latest On HIV Vaccine Research?

Scientists are continuing to create and test HIV vaccines—in the lab, in animals, and even in human subjects. These vaccine trials help researchers to learn whether a vaccine will work and if it can be safely given to people.

In 2009, MHRP and collaborating researchers published findings from a large-scale HIV vaccine trial in Thailand called RV144. That trial involved more than 16,000 adults and showed that a combination vaccine was safe and could prevent about 32 percent of new infections. The scientific community, with leadership from NIAID, is working collaboratively to build on what was learned from RV144 in order to help speed the process of finding an HIV vaccine. Those efforts have provided information that certain antibodies (proteins produced by the body to fight infection) may serve either as a signal or provide a direct role to decreasing the risk of becoming HIV infected. This has led to a better understanding of the type of immune response that may be needed for a preventive HIV vaccine to be effective. For more information on the Thailand vaccine trial, see the U.S. Military HIV Research Program.

Prevention Research

Related Topics on AIDS.gov

Frequently Asked Questions

How can I participate in an HIV vaccine trial?

For more information about HIV vaccines and how you can get involved in HIV vaccine trials, check out Be The Generation. For information about specific HIV vaccine trials, go to the HVTN website at www.HVTN.org or http://www.AIDSinfo.nih.gov, which has information about all HIV trials.

Can I get HIV from participating in a vaccine clinical trial?

No. You can’t get HIV infection from participating in a vaccine trial because the vaccines being tested do not contain the virus itself.